The present invention generally relates to multiple chamber pistons, and more particularly, the present invention relates to multiple chamber pistons having a high compliance to accommodate lower frequencies.
Presently, multiple chamber pistons are used for a plurality of damping applications on a vehicle, including engine mounting and suspension applications. Typically, this cylindrical device has an outer cylindrical surface attached to an unsprung mass, such as the vehicle axle, and the center portion attached to a sprung mass, such as the vehicle body. Additionally, the unsprung mass can be the vehicle engine with the vehicle body being the unsprung mass, thereby attenuating vibrations from the vehicle engine to the vehicle body. Multiple chamber pistons utilize at least two separate passages connecting two separate chambers within the device to attenuate and absorb undesirable vibrations. Each passage connecting respective chambers is tuned by adjusting the overall length and area of the passage. Typically, the lengths and cross sectional areas are chosen to attenuate frequencies of below 20 hertz. Accordingly, the longer and narrower the passage is, the lower the frequency the device attenuates. As a result, it is desirable to provide long and narrow passages within these devices to attenuate low frequencies.
While the present state of the art serves to absorb unwanted vibrations in vehicles, some drawbacks exist. Specifically, during manufacturing, long and narrow passages are often difficult to manufacture. Manufacturing such passages requires the manufacturing processes to hold tight tolerances. And, because the surrounding walls are often an elastomeric material, the possibility of passage collapse increases as the passage is made more narrow. Moreover, longer passages require more distance through the device. As these devices are typically limited in size, it is not always possible to provide a long length passage. The present invention was developed in light of these and other draw backs.
In light of these and other drawbacks, the present invention provides a multiple chamber piston for attenuating vibrations in a vehicle that includes a bushing having a first fluid chamber connected to a second fluid chamber by a first channel. The bushing includes a third fluid chamber connected to a fourth fluid chamber by a second channel. The first fluid chamber and the third fluid chamber are separated by an air chamber. The second fluid chamber and the fourth fluid chamber are separated by a second air chamber.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.